Conventional broadloom tufting machines designed for manufacturing carpet and artificial athletic turf in high volume are primarily characterized by having cooperating backing feed and tufting head assemblies. Typically, such a backing feed assembly is defined by an arrangement of feed and take-up rollers that convey an elongate sheet of backing fabric through a tufting zone area in which yarn is inserted into the steppedly advancing backing. Differential rotation between feed assembly rollers stationed at opposing ends of the tufting zone creates longitudinal tension in the backing.
The tufting head portion of the broadloom machine generally features one or more elongate bars of yarn-delivering needles which are disposed above the horizontal backing and aligned transverse to the direction of its movement, as well as an equivalent number of yarn-catching loopers that are disposed below the backing. Needles along the needle bar(s) each receive yarn, delivered by any of a variety of suitable yarn feed mechanisms, from a designated spool situated within a yarn creel. So, as the backing sheet travels past the tufting head, needle bars are continually reciprocated downward so that the needles along them penetrate and insert yarn into the backing in unison. The loopers operate in synchronicity with the needles such that, as each needle momentarily protrudes the backing, a corresponding looper catches its yarn before the needle returns upward. This repeated interaction produces “loop pile” tufts of yarn along the backing. Additionally, knives can be used to sever just-formed loops and thereby render “cut pile” tufts.
Where uniformly patterned carpet or vast monochrome sections of athletic turf are to be produced in high volume, a broadloom tufting machine's needle can span the entire transverse width of the backing material. The incremental, longitudinal progression of the backing material that immediately follows each stroke of the needle bar causes the laterally-aligned needles to form every longitudinal running row of tufts intended to be created across the lateral length of the backing sheet. Thus, the tufting needles stationed along the needle bar remain at constant lateral positions, and there is no need for them to be transversely shifted when creating carpet or turf sections having uniform tuft placement and yarn color. On the other hand, tufting machines exhibiting constant axis needle bar movement are generally not suitable for producing multicolored articles of tufted material. So, the prior art has seen tufting machines improved to enable their needle bars to shift laterally, relative to the backing, in order that the particular type of yarn delivered by particular individual needles be selectively inserted into the backing at specific tuft locations in accordance with a preconceived pattern. For example, U.S. Pat. No. 4,829,917 to Morgante, et al. discloses the use of a computer-controlled hydraulic actuator for shifting a needle bar into different lateral positions in response to pre-selected stitch pattern information stored in the computer. As another example, U.S. Pat. No. 5,979,344 to Christman, Jr. discloses the use of computer-controlled inverse roller screw actuators for shifting needle bars laterally, as well as for shifting the backing sheet itself laterally, in order to tuft a graphic pattern of yarn into the backing as it advances longitudinally past transversely aligned needles.
Nevertheless, even with the lateral shiftability of their tufting heads, these prior tufting machines that employ backing feed mechanisms are still not optimum for producing precise, dynamic, multicolored tuft patterns like those often found in artistic logo-bearing sections of artificial athletic turf. That is, firstly, because the synchronous reciprocation of their bar-mounted needles produces linear color patterns, and even lateral shifting of the needle bars can no more than produce diagonal or zigzagging patterns. In addition, since conventional tufting machines with backing feed mechanisms experience many subtle operational irregularities in the cooperative motions of their tufting head and backing feed components, the tuft patterns that they create tend to be imprecise.
More specifically, tufting needles of prior art backing fed tufting machines reciprocate (along Z-axes) and may shift (along an X-axis) in timed relationship with the stepped longitudinal progression (along a Y-axis) of the backing fabric being fed past those needles. Whenever that three-axis motion relationship is altered in an unplanned way, the tufting needles fail to insert yarn tufts precisely at intended positions. For example, any sudden lag or surge in the feed mechanism's operation can create irregularity in the longitudinal spacing between successive tufts within rows, and any lateral skewing of the backing sheet can displace tuft rows entirely. The result of either occurrence may be noticeable distortion of the overall graphic image being created.
Moreover, inherent characteristics of backing material itself tends to undermine the quality of graphic output of these prior art machines. To wit, because backing sheets are typically fabricated of coarsely woven material, they are susceptible to being non-uniformly stretched, in either direction, as feed rollers advance them through the tufting zone. Since athletic field logos are almost always too large to be entirely formed within the lateral boundaries of a machine's tufting zone—which is typically no more than 15 feet wide they must be created in pieces by individually tufting separate sheets of backing material and then gluing those sheets, side-by-side, onto a base layer material. This leaves open the possibility that one image-bearing section of backing will progress through the tufting zone differently, in some respect, than does an adjacently laid section and will, in turn, manifest as color discontinuity within the composite image that is visible upon installation. Therefore, in the process of tufting separate graphically patterned artificial turf pieces for a single installation, there is a premium on being able to ensure that tension applied to backing material remains consistent and that no unwanted lateral movement occurs within the tufting zone.
Tufting head assemblies that operate while moving two-directionally relative to statically held backing sheets have been developed in the prior art to address these stability concerns related to production of detailed tuft patterns. For example, U.S. Pat. No. 5,743,200 to Miller, et al. discloses a tufting machine that employs a gantry-like component which is movable along a Y-axis and which carries a tufting head that is movable along an X-axis. The Miller tufting head is disposed above the backing material, and it is mounted to the gantry via its attachment to a frame which is gearably connected to and movable along the gantry. The tufting head generally comprises a cylinder that is slidably secured to the frame, a piston that reciprocates within the cylinder, a needle that is secured to the bottom end of the cylinder and a blade that is positioned within the needle and is secured to the bottom of the piston. The blade projects from and retracts into the needle to assist the needle in protruding down through the backing to form loop pile tufts therein. The Miller tufting machine also includes a second, lower gantry that spans transversely below the backing material and moves along a Y-axis in synchronicity with the upper gantry. This lower gantry provides underlying support for the backing material in order to limit the downward deflection that would otherwise result from the pressure applied by the blade and needle operating on the backing.
Another example is found in U.S. Pat. No. 7,814,850 to the present inventor. That patent discloses a tufting machine with a dual-beam gantry configuration and that includes a computer-controlled tufting head adapted to move along X and Y axes in order to insert various yarns at precise locations along a clamped down and statically held backing in accordance with a design pattern stored in the computer. It also discloses a tufting head for producing precise graphic tuft patterns that is defined by having two distinct and asynchronously driven parts: (a) a needle carriage that is movably mounted along the upper gantry beam (i.e., above the backing) and features a number of separately operating tufting needles that are selectively reciprocated to insert tufts as the carriage journeys along an X-axis; and (b) a looper carriage that is movably mounted to the lower beam (i.e., below the backing) and is not mechanically connected to the needle carriage, but rather is selectively advanced to and fro along that beam in non-unison with the needle carriage such that a single looper and cutter pair may selectively cooperate with each one of multiple carriage needles as they individually downstroke.
Nevertheless, while these fixed backing type tufting machine configurations allow for proper tensioning and stabilization of backing pieces to be practiced repeatedly, they do not lend themselves to high production throughput. In fact, the exercise of manually removing and replacing backing sheets for successive tufting, alone, makes these kinds of machines impractical for creating anything other than a relatively small section of an athletic field bearing a graphic design. Consequently, the larger “green areas” of turf are typically produced entirely separate from the design areas by feeding separate rolls of backing material through conventional broadloom machines. In some instances, this phenomenon has led to athletic field turf manufacturers having to invest in more machinery in order to be able to produce all of the tufted backing strips needed for an entire field installation. In other instances, it has led to turf purchasers ordering tufted parts of a single field installation from separate manufacturing vendors: one specializing in high throughput production of the larger green sections and another specializing in production of smaller graphic image sections. Furthermore, regardless of whom does the manufacturing, installers are burdened with having to carefully piece potentially numerous backing pieces together at abuse surface, rather than unrolling onto a base a relative few field long rolls of backing.
Accordingly, the present invention a longstanding need for a tufting machine configured to produce continuous, lengthy sections of graphic and non-graphic athletic turf under conditions of backing stability achieved by previous fixed backing machines, but at a throughput rate more approaching that achieved by previous machines utilizing less stable backing feed assemblies. The tufting machine of the present invention substantially fulfills this need.